Process and apparatus for contamination-free processing of semiconductor parts

ABSTRACT

This invention relates generally to a process and apparatus for contamination-free processing of semiconductor parts. More specifically, this invention relates to a process and apparatus for contamination-free processing of semiconductor parts in an oven or a furnace. This invention also relates to a process and apparatus for contamination-free processing of semiconductor parts in a furnace, such as a belt type furnace that sequentially stops the belt at the vicinity of at least one heating or cooling unit to heat or cool the part.

CROSS-REFERENCE TO A RELATED PATENT APPLICATION

This patent application is a Continuation of U.S. patent applicationSer. No. 08/227,937, filed on Apr. 15, 1994, which issued as U.S. Pat.No. 5,471,033, on Nov. 28, 1995.

FIELD OF THE INVENTION

This invention relates generally to a process and apparatus forcontamination-free processing of semiconductor parts. More specifically,this invention relates to a process and apparatus for contamination-freeprocessing of semiconductor parts in an oven or a furnace. Thisinvention also relates to a process and apparatus for contamination-freeprocessing of semiconductor parts in a furnace, such as a belt typefurnace that sequentially stops the belt at the vicinity of at least oneheating or cooling unit to heat or cool the part.

BACKGROUND OF THE INVENTION

For many years the electronics or semi-conductor industry has been usingvarious types of ovens and furnaces for high volume heating and/orcooling applications. In the oven and furnace industry many inventionshave occurred. However, most of them have been directed to innovationsin either cooling or heating of the parts that are being processed.

U.S. Pat. No. 4,554,437 (Wagner et al.) discloses a continuous speedbelt type tunnel oven which allows a user to select different top andbottom temperatures within each of the plural cooking zones.

U.S. Pat. No. 4,693,211 (Ogami et al.) discloses a surface treatmentapparatus, which is composed of a supporting die for holding a substratethereon to heat and/or cool the substrate. A cover defines a treatmentspace over the entire surface of the substrate on the supporting die.Preferably, a heat-insulating housing could be outside the cover.

U.S. Pat. No. 4,886,954 (Yu et al.) discloses a hot wall diffusionfurnace and a method for operating the furnace. Yu et al. disclose thatthe heating elements in the upper section of the furnace be connected toone circuit, and the heating elements of the lower section of thefurnace be connected to a second circuit, and that each circuit becontrolled in response to the temperature in that section, so thatuniform temperature can be obtained in the processing chamber.

U.S. Pat. No. 4,903,754 (Hirscher) discloses a method and apparatus forthe transmission heat to or from plate like object. The plate-likeobject, such as a Si wafer, is held on a back plate and inside a cover.This patent discloses both the heating and cooling of the plate-likeobject.

U.S. Pat. No. 4,950,870 (Mitsuhashi et al.) discloses a heat-treatingapparatus having at least three heaters and the power to these heaterscan be supplied from independent power sources so that the heatingtemperatures of the individual heaters can be freely adjusted.Additionally, the multiple heaters in the vertical furnace attain auniform heat distribution throughout the heating zone.

U.S. Pat. No. 4,966,547 (Okuyama et al.) discloses a heat treatmentmethod using a zoned tunnel furnace. The furnace has roller conveyer andeach of the zones in the furnace walls are provided with electricresistance heating wires. The heaters in each zone are under programmedcontrol, independent of the heaters in the other zones. Similarly, theroller conveyer in each zone can be driven independent of the rollerconveyer in the other zones by programmable controllers.

U.S. Pat. No. 4,982,347 (Rackerby et al.) discloses a process andapparatus for producing temperature profiles in a workpiece as it passesthrough a belt furnace. Each of the heaters has their own separatethermostats, which enables the temperature of each heater to beseparately set. Thus a workpiece can be subjected to a temperatureprofile which varies from heater to heater along the passageway.

U.S. Pat. No. 5,054,418 (Thompson et al.) discloses a device for holdingwafers of semi-conducting materials during thermal processing orcoating, where the device is a cage boat having removable slats.

The parts or products using conventional furnaces and ovens have changedover time. Some of the parts have been getting larger and others aregetting smaller, and still other require more stringent processingcontrols. Therefore, it has become increasingly difficult to do the sametype of processing on the parts, as done by the ovens and furnaces knownin the art.

For some parts the thermal mass or thermal weight resists being heatedquickly, and therefore they may have to be processed for a longerperiod. Another factor is that newer and different materials are beingused to make these parts, and these newer materials require differentheating regimes. These issues are further compounded by the fact thatnow closer temperature control and lower intra-part gradients are beingrequired by the electronics industry.

The manufacturers of conventional ovens and furnaces have made quite afew upgrades to their system in response to the industrial needs. Someupgrades include providing better and more efficient gas flows. Othershave provided improved zone separation. And, still others are providingbetter cooling in the cool down section. Most of these changes arerequired because the parts or products are less tolerant to thermalprocess irregularities and the resultant mechanical stresses, etc.

Another problem faced in the use of conventional ovens or furnaces isthat when flux or similar contaminants are used in a conventional ovenor furnace they get deposited on the walls of the furnace creating acontamination problem for the furnace as well as the parts that arebeing processed in the furnace. Flux and similar contaminants resultsfrom many processes, such as a soldering process, and therefore cannotbe eliminated. Similarly, there are other solvents which evaporate fromthe surface of the part, as the part is being heated, and they enter theflow of the gases in the furnace, flowing from the hotter end or area toa colder area. This causes the vaporized solvents and similar othermaterial to condense on cooler furnace areas or parts and this collectsas contamination.

For an application, such as chip join, the operation is characterized byloading many parts on a belt, followed by continuous movement of thebelt through the furnace's heating and/or cooling areas, and thus it isnot very practical to stop and clean the furnace for a different partand/or a different process.

Therefore, during a typical high volume heating and/or coolingapplications care must be taken to prevent the parts being processedfrom being contaminated with contaminants that are inside the furnace,and that the contamination be kept to the minimum.

For the above-mentioned reasons, parts cannot always be processed withinspecification using the conventional ovens or furnaces, and thereforethere is a need for improvement in the furnace and oven industry.

The above-mentioned and other problems have been overcome by the novelapparatus and the process of this invention.

BRIEF SUMMARY OF THE INVENTION

In one aspect the invention comprises a process for processing a part ina contaminating environment wherein said part is protected from saidcontamination, comprising the steps of:

(a) placing said part on a part carrier in a first environment,

(b) placing a cover over said part carrier and enveloping said part soas to form a boat,

(c) removing said boat from said first environment,

(d) placing said boat in a second, more contaminating, environment andprocessing said part.

In another aspect the invention comprises an apparatus for processing atleast one part comprising a covered boat enveloping said part and havinga first environment while said apparatus having a second morecontaminating environment, wherein said covered boat is placed insidesaid apparatus and further comprising at least one means for processingsaid part.

PURPOSES OF THE INVENTION

One purpose of this invention is to provide a process that is veryeconomical.

Another purpose of the invention is to provide a process that is easilyadaptable to the existing ovens and furnaces.

Still another purpose of this invention is to provide a system thattransports the parts through a contaminating environment withoutcontaminating the part.

Yet another purpose of this invention is to process the part such thatthe part is itself in a less contaminated environment than itssurroundings.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the invention believed to be novel and the elementscharacteristic of the invention are set forth with particularity in theappended claims. The figures are for illustration purposes only and arenot drawn to scale. The invention may be best understood by thedescription which follows, taken in conjunction with the accompanyingdrawings in which:

FIG. 1, is a perspective view of a preferred embodiment of the presentinvention.

FIG. 2, is a perspective view showing another embodiment of the presentinvention.

FIG. 3A, is a perspective view showing yet another embodiment of thepresent invention.

FIG. 3B, is a sectional view taken along section 3B--3B of FIG. 3A.

FIG. 4, is a cross-sectional view of still another embodiment of thepresent invention.

FIG. 5, is a cross-sectional view of still yet another embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

The preferred embodiment of the invention is illustrated in FIG. 1,where a part or a substrate 10, to be processed is placed on a base 12,and is protected from the environment by a cover 14. The base 12, havingan upper surface 18, is typically made from quartz, glass, metal, etc.Similarly, it is preferred that the cover 14, having peripheral baseedge 28, be also made from quartz, glass, metal, to name a few.

In a typical application the substrate 10, is placed on the uppersurface 18, of the base 12, for example, in a Class 10 clean room, andthen the cover 14, is subsequently placed to protect the substrate 10,in the same Class 10 clean room. A Class 10 clean room, for example, isa room or area where there are less than 10 particles of not greaterthan 0.3 micron particle size per cubic foot of air. This way thecontamination inside the cover is Class 10, and there is no reason tocreate a vacuum inside the cover 14, to keep the area inside the cover14, and over and around the substrate 10, contamination free. The base12, along with the cover 14, will be referred to as a parts carrier orboat 20.

For some applications it may be necessary to create a vacuum or extractcertain contaminants out of under the cover 14, and keep the substrate10, in a contamination free environment. This can be done as illustratedin FIG. 2, where a boat 40, having a cover 24, has at least one vent orplug 16, through which the contaminating gases and/or particles could beextracted. Of course this vent or plug 16, could be on the top of thecover 24, or could be a part of the base 12. The vent or plug 16, couldalso be used to prevent the creation of a pressure differential betweeninside and outside of the boat.

FIG. 2, also illustrates that the substrate 10, could also be placed ona substrate or part pedestal or support 22. The substrate pedestal 22,allows the part or substrate 10, to be processed without the need tohave the substrate 10, itself be physically moved. For some applicationsthe substrate 10, could be secured to the substrate pedestal 22, bymeans well known in the art, such as, screws, bolts, clamps, etc.

FIG. 3A, is a perspective view showing yet another embodiment of thepresent invention, while FIG. 3B is a sectional view taken along section3B--3B of FIG. 3A. A boat or parts carrier 60, has a base 32, having agroove or a trench or channel 30, to accommodate the peripheral baseedge 28, of the cover 14. The base edge 28, could have rectangular-typeshape or circular-type shape or polygonal-type shape or atriangular-type shape, to name a few. Of course the trench or channel30, in the base 32, should have a shape complementary to that of thebase edge 28, to provide the maximum seal or contamination freeenvironment to the part 10.

For some applications it may be necessary to put a seal or similar suchmedia between the base edge 28, and the upper surface 18, of the base 12or 32. Typical seals that are used in the industry are seals made fromsilicon or polymers, to name a few.

FIG. 4, illustrates a cross-sectional view of a boat or parts carrier80, which is still another embodiment of the present invention. The boat80, typically has a pan-shaped base 42, having side-walls 44. The part10, to be processed could be placed on a support or pedestal 46, havinga plurality of posts or stand-offs 48. Cover 54, having ledge 56, isthen used to provide a cover for the part 10, and posts or stand-offs45, typically, separate the cover 54, from the base 42. For someapplications, the stand-offs 45 and/or 48, could be made from materialthat allows the movement of fluid through it. This movement of fluid,such as air, of course will prevent or reduce any pressure differentialthat might exist between the inside and outside of the boat 80.

FIG. 5, is a cross-sectional view of still yet another embodiment of thepresent invention showing a boat or parts carrier 100. The boat 100, hasa pan-shaped base 62, having side-walls 64. The base 62 and theside-walls 64, could have one or more electrical implants, such as,resistance thermal heater 65, to provide local thermal heating to thepart 10, which may be on a plurality of posts or stand-offs 48. A cover74, having ledge 76, could also have at least one electrical implant orresistance thermal heater 75, to provide local thermal heating to thepart 10. The boat 100, could also have one or more breathers or vents66, to allow for the part to "breathe" or to prevent a pressuredifferential from occurring inside the boat 100. In some cases the boat100, could of course itself be placed inside an oven for furtherprocessing of the part 10.

The boat 20, 40, 60 or 80, along with the substrate 10, is typicallyplaced in an oven or furnace or a cooling environment and the processingof the part 10, continues.

As will be appreciated that now, for example, the boat 20, can be placedin an oven or a furnace (not shown) that has, for example, a Class 100or Class 1000 or more environment but the part 10, being in the boat 20,will not be exposed to the outside contamination, and will only see thecleaner, for example, Class 10, environment.

The boat or parts carrier 20, 40, 60 or 80, could also be placed on asequential belt type furnace, as disclosed in U.S. patent applicationSer. No. 07/920,948, entitled "Sequential Step Belt Furnace WithIndividual Concentric Heating Elements", assigned to the assignee of theinstant patent application and the disclosure of which is incorporatedherein by reference, and the part 10, could be processed without beingcontaminated by carrier gasses that might exist in a belt type furnace.

Similarly, the boat or parts carrier 20, 40, 60, 80 or 100, could alsobe placed on a sequential belt type furnace, as disclosed in U.S. patentapplication Ser. No. 08/218,105, filed on Mar. 25, 1994, now U.S. Pat.No. 5,421,723, entitled "Sequential Step Belt Furnace With IndividualConcentric Cooling Elements" assigned to the assignee of the instantpatent application and the disclosure of which is incorporated herein byreference, and the part 10, could be processed without beingcontaminated by the contaminants that might exist in the furnace.

The part 10, could be an I. C. (Integrated Circuit) chip or asemiconductor substrate or a semiconductor module, or similar suchproduct.

It has been found that the parts 10, described in this invention, couldbe large parts, such as ceramic substrates which are typically about 100mm by 100 mm to about 20 mm by 20 mm or smaller parts, such assemiconductor chips which are typically about 10 mm by 10 mm.

The heating or "cooling" is typically provided to the boat 20, 40, 60,80 or 100, and in-turn to the part 10, by one or more of the upper,lower or side heating or cooling units in a furnace.

If a sequential belt type furnace is used then the boat 20, 40, 60 or80, is typically accelerated, and then decelerates, and the part 10, isplaced typically in the center of the heating or cooling zone. Ofcourse, using a computer or a controller one could program or control ormonitor the transit or soak times or the belt speeds, etc.

Using the inventive boat 20, 40, 60, 80 or 100, the contaminating gasesor particles or evaporated flux that may exist in an oven or a furnace,never gets an opportunity to condense on the surface of the part.

As one can see that the process and apparatus of this invention providesa substantial improvement over the state of the art.

This inventive furnace can be used for a variety of processes, forexample, pin brazing process, chip join process, C4 (Controlled CollapseChip Connection) bonding, to name a few. (C4 and Controlled CollapseChip Connection are Trademarks of IBM Corporation, Armonk, N.Y., USA.)

The thermally conductive closed boat or container of this inventionprovides isolation of the product and shields it from contamination thatis generated, such as from the surrounding environment, processingmachinery, etc.

The invention also provides a mean to uniformly heat the part whileshielding it from the contaminants.

It has also been discovered that the boat or parts carrier having alimited number of holes or openings or vents or material that allow forlimited amount of fluid flow does not have any major adverse affect onthe part being processed. As a matter of fact the amount of contaminantsin a fully sealed boat was not any lower than a similar boat withlimited vents that allowed for limited fluid flow.

EXAMPLES

The following examples are intended to further illustrate the inventionand are not intended to limit the scope of the invention in any manner.

Example 1

A large sized semiconductor substrate A, was placed inside acontamination control box and then covered. The covered container wasthen placed inside a Blue M oven and the substrate A was baked atapproximately 400° C. After the processing of substrate A, a surfaceparticle count was made and it was found that the surface of substrateA, had 1,228 particles. A similar substrate B, was also processed in thesame Blue M oven under the same processing conditions, but on an openboat, and upon inspection a total of 2,312 particles were counted on thesurface of substrate B. This is an increase of 1,084 particles after thebaking step.

Example 2

A medium sized semiconductor substrate C, was placed inside acontamination control box and then covered. The covered container wasthen placed inside a Blue M oven and the substrate C, was baked atapproximately 400° Centigrade. After the processing of substrate C, asurface particle count was made and it was found that the surface ofsubstrate C, had 221 particles. A similar substrate D, was alsoprocessed in the same Blue M oven under the same processing conditions,but on an open boat, and upon inspection a total of 333 particles werecounted on the surface of substrate D. This is an increase of 112particles after the baking step. The surface of both parts C and D, hada coating of a layer of polyimide.

Example 3

A small sized semiconductor substrate E, was placed inside acontamination control box and then covered. The covered container wasthen placed inside a Blue M oven and the substrate E, was baked atapproximately 400° Centigrade. After the processing of substrate E, asurface particle count was made and it was found that the surface ofsubstrate E, had 190 particles. A similar substrate F, was alsoprocessed in the same Blue M oven under the same processing conditions,but on an open boat, and upon inspection a total of 257 particles werecounted on the surface of substrate F. This is an increase of 67particles after the baking step. The surface of both parts E and F, hada coating of a layer of approximately 200 angstroms of chromium.

While the present invention has been particularly described, inconjunction with a specific preferred embodiment, it is evident thatmany alternatives, modifications and variations will be apparent tothose skilled in the art in light of the foregoing description. It istherefore contemplated that the appended claims will embrace any suchalternatives, modifications and variations as falling within the truescope and spirit of the present invention.

What is claimed is:
 1. A process for treating a part in a secondenvironment wherein said part is protected from said second environment,comprising the steps of:(a) placing said part on a part carrier in afirst environment, (b) placing a cover over said part carrier such thatsaid cover entraps material from said first environment while envelopingsaid part to form a covered boat, (c) removing said boat from said firstenvironment, and (d) placing said boat in said second environment fortreating said part wherein said second environment has morecontamination than said first environment.
 2. The process of claim 1,wherein said first environment is less than class 100 and said secondenvironment is at least class
 100. 3. The process of claim 1, whereinsaid part carrier is selected from a group consisting of glass, metaland quartz.
 4. The process of claim 1, wherein said cover is selectedfrom a group consisting of glass, metal and quartz.
 5. The process ofclaim 1, wherein said second environment is at least class
 10. 6. Theprocess of claim 1, wherein said second environment is a furnace.
 7. Theprocess of claim 6, wherein said furnace is selected from a groupconsisting of a vertical furnace, a continuous belt furnace and asequential belt furnace.
 8. The process of claim 1, wherein said part isselected from a group consisting of a semiconductor chip, asemiconductor module and a semiconductor substrate.
 9. The process ofclaim 1, wherein said part is secured to a pedestal on said partcarrier.
 10. The process of claim 1, wherein said part carrier has atleast one trench to accommodate a peripheral base edge of said cover.11. The process of claim 1, wherein said boat has at least oneelectrical implant to thermally heat said part.
 12. The process of claim1, wherein said boat has at least one opening to prevent a pressuredifferential from occurring inside said boat.